/*
 * Copyright 2002-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.http.codec.multipart;

import org.springframework.core.ResolvableType;
import org.springframework.core.codec.Hints;
import org.springframework.core.log.LogFormatUtils;
import org.springframework.http.MediaType;
import org.springframework.http.ReactiveHttpInputMessage;
import org.springframework.http.codec.HttpMessageReader;
import org.springframework.http.codec.LoggingCodecSupport;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

import java.util.*;
import java.util.stream.Collectors;

/**
 * {@code HttpMessageReader} for reading {@code "multipart/form-data"} requests
 * into a {@code MultiValueMap<String, Part>}.
 *
 * <p>Note that this reader depends on access to an
 * {@code HttpMessageReader<Part>} for the actual parsing of multipart content.
 * The purpose of this reader is to collect the parts into a map.
 *
 * @author Rossen Stoyanchev
 * @since 5.0
 */
public class MultipartHttpMessageReader extends LoggingCodecSupport
        implements HttpMessageReader<MultiValueMap<String, Part>> {

    private static final ResolvableType MULTIPART_VALUE_TYPE = ResolvableType.forClassWithGenerics(
            MultiValueMap.class, String.class, Part.class);


    private final HttpMessageReader<Part> partReader;


    public MultipartHttpMessageReader(HttpMessageReader<Part> partReader) {
        Assert.notNull(partReader, "'partReader' is required");
        this.partReader = partReader;
    }


    /**
     * Return the configured parts reader.
     *
     * @since 5.1.11
     */
    public HttpMessageReader<Part> getPartReader() {
        return this.partReader;
    }

    @Override
    public List<MediaType> getReadableMediaTypes() {
        return Collections.singletonList(MediaType.MULTIPART_FORM_DATA);
    }

    @Override
    public boolean canRead(ResolvableType elementType, @Nullable MediaType mediaType) {
        return MULTIPART_VALUE_TYPE.isAssignableFrom(elementType) &&
                (mediaType == null || MediaType.MULTIPART_FORM_DATA.isCompatibleWith(mediaType));
    }


    @Override
    public Flux<MultiValueMap<String, Part>> read(ResolvableType elementType,
                                                  ReactiveHttpInputMessage message, Map<String, Object> hints) {

        return Flux.from(readMono(elementType, message, hints));
    }


    @Override
    public Mono<MultiValueMap<String, Part>> readMono(ResolvableType elementType,
                                                      ReactiveHttpInputMessage inputMessage, Map<String, Object> hints) {

        Map<String, Object> allHints = Hints.merge(hints, Hints.SUPPRESS_LOGGING_HINT, true);

        return this.partReader.read(elementType, inputMessage, allHints)
                .collectMultimap(Part::name)
                .doOnNext(map ->
                        LogFormatUtils.traceDebug(logger, traceOn -> Hints.getLogPrefix(hints) + "Parsed " +
                                (isEnableLoggingRequestDetails() ?
                                        LogFormatUtils.formatValue(map, !traceOn) :
                                        "parts " + map.keySet() + " (content masked)")))
                .map(this::toMultiValueMap);
    }

    private LinkedMultiValueMap<String, Part> toMultiValueMap(Map<String, Collection<Part>> map) {
        return new LinkedMultiValueMap<>(map.entrySet().stream()
                .collect(Collectors.toMap(Map.Entry::getKey, e -> toList(e.getValue()))));
    }

    private List<Part> toList(Collection<Part> collection) {
        return collection instanceof List ? (List<Part>) collection : new ArrayList<>(collection);
    }

}
